1. Field of the Invention
This invention relates to a cassette mounting device for mounting and demounting a cassette on and from the body of a recording and/or reproducing apparatus such as a VTR by moving a cassette holder up and down, and also relates to a recording and/or reproducing apparatus provided with such a cassette mounting device.
2. Description of the Related Art
Cassette mounting devices which have heretofore been arranged to mount and demount a tape cassette on and from the body of, say, an 8 mm VTR or the like car be divided into two types. One is an automatic loading (or front loading) type which is arranged to be used for an installed type VTR and which is provided with a drive source. The other is a pop-up type which is arranged to be used for a camera-integrated type VTR and to be rendered operative when a cassette holder is pushed down by the operator of the VTR.
In the case of the latter pop-up type cassette mounting device, the simplification of mechanism and the reduction in weight thereof have advanced according to the recent trend of the reduction in size of the camera-integrated type VTR or the like and, as a result, the cassette mounting device has come to be usually arranged to have a lock mechanism for locking the cassette holder in its lowered position only on one side of the cassette holder. This arrangement is called a single-side(d lock type. However, since such a single-sided lock type cassette mounting device has an arrangement in which the pushing-down force is applied to the cassette holder directly by the operator, the reduction in size and weight has come to cause difficulty in arranging t-he cassette mounting device to adequately keep its function and strength and to give an adequate feeling of operation thereon.
FIGS. 6(a) and 6(b) to FIGS. 9(a) and 9(b) show the conventional cassette mounting device. Of these figures, FIG. 6(a) shows the cassette holder in its raised (popped-up) state. FIG. 6(b) shows the cassette holder in its lowered (locked) state. FIG. 7 is a top view of the whole cassette mounting device. The conventional cassette mounting device is described below with reference to those figures.
The illustrations include a tape cassette 1, a magnetic tape 2 contained within the tape cassette 1, and a main chassis 3 of a VTR body. A rotary drum 4 which has a plurality of recording/reproducing heads is disposed on the main chassis 3. A sliding chassis 5 is arranged to be slidable over the main chassis 3. A cassette holder 6 is arranged to allow the tape cassette 1 to be inserted therein. First and second levers 7 and 8 form X-shaped links on both sides of the cassette holder 6. A fulcrum shaft 9 is arranged in each of the X-shaped links to rotatably connect the first and second levers 7 and 8 to each other. A connection shaft 10 is arranged to interconnect one ends of the first levers 7 dispose(d on both sides of the cassette holder 6 for synchronizing the phases of the X-shaped links on the two sides and also serves to swingably support the first levers 7 on the cassette holder 6. A shaft pin 11 is disposed at the other end of each of the first levers 7. A cam slot 12 is formed in each of the side plates of the sliding chassis 5. The shaft pin 11 is engaging the cam slot 12. A shaft pin 13 is disposed at one end of each of the second levers 8 and is rotatably supported by each corresponding side plate of the sliding chassis 5. A cam slot 14 is formed in the other end of each of the second levers 8. A shaft pin 15 is arranged on each side plate of the cassette holder 6 to slidably engage the cam slot 14. A tension spring 16 stretches between each pair of the first and second levers 7 and 8 to exert an urging force for moving the cassette holder 6 up. Cassette retaining springs 17 are provided on the upper surface of the cassette holder 6. There is also provided a lid opener 18 for opening a lid 1a of the tape cassette 1.
Reel mounts 19 are disposed on the sliding chassis 5.
When the cassette holder 6 is pushed down against the force of the springs 16 after insertion of the tape cassette 1 into the cassette holder 6 in the popped-up state as shown in FIG. 6(a), the cassette holder 6 comes to its lowered position, as shown in FIG. 6(b), where the cassette holder 6 is locked and kept in the locked state by a lock mechanism 20, which is disposed on the side opposite to the illustrated side. The lid 1a of the tape cassette 1 is opened by the lid opener 18 while the cassette holder 6 is being moved down. With the cassette holder 6 in the locked state, the tape cassette 1 is mounted on the reel mounts 19 of the sliding chassis 5, while the cassette retaining springs 17 push the tape cassette 1 from above. After that, the sliding chassis 5 is slid in the direction of approaching the rotary drum 4 and, at the same time, the tape 2 is pulled out from the tape cassette 1 by means of a loading mechanism which is not shown. By this, at least a part of the rotary drum 4 is relatively inserted into an opening part of the cassette 1 in such a way as to have a portion of the tape 2 wrapped around the circumferential surface of the rotary drum 4. The tape 2 is then allowed to travel and signals are recorded or reproduced by the recording/reproducing heads of the rotary drum 4. In taking out the tape cassette 1, the operation is performed in the order reverse to the above-stated operation. When the sliding chassis 5 is slid in the direction of going away from the rotary drum 4, the tape 2 is rewound up into the tape cassette 1. After that, the cassette holder 6 is unlocked by an eject mechanism which is not shown. The X-shaped links are operated by the force of the springs 16 to move up the cassette holder 6 into the popped-up position as shown in FIG. 6(a).
The lock mechanism 20 is generally provided only on one side of the cassette holder 6, as mentioned above, for the purpose of reduction in size and weight of the cassette mounting device. Such being the arrangement, a positioning action on the side opposite to the locking side is carried out by causing the first and second levers 7 and 8 on this side to follow the phases of the first and second levers 7 and 8 disposed on the locking side, by means of the rigidity of the connection shaft 10 and the cassette holder 6. FIG. 8 shows, in an oblique view, how this positioning action of the link mechanism is carried out, in a simplified manner, omitting the cassette holder 6 from the drawing. The X-shaped link (the first and second levers 7 and 8) on the side opposite to the locking side is arranged to receive a lifting force which is a resultant force resulting from the lifting force of the springs 16, a reaction force caused by the cassette retaining springs 17 and a reaction force caused by a lid closing spring of the lid 1a of the tape cassette 1, and to suppress the resultant force mainly by the rigidity of the connection shaft 10.
FIGS. 9(a) and 9(b) are side views showing how a force is exerted on the side opposite to the locking side. In these figures, the link mechanism and parts therearound are shown in a simplified manner to facilitate understanding. FIG. 9(a) shows the popped-up state and FIG. 9(b) shows the locked state of the cassette holder 6. In the single-sided lock type cassette mounting device, the cassette holding action on the side opposite to the lock mechanism 20 is performed, as mentioned above, through the connection of the right and left links made, as mentioned above, mainly by the connection shaft 10 and the first levers 7. To prevent the tape cassette 1 from being inadequately held due to looseness of fitting engagement of the shaft pin 11, the cam slot 12, etc., and an inadequate machining precision, it is generally practiced to provide a phase difference in interconnecting the first levers 7 and 7' which are respectively disposed on the locking side and the non-locking side. In FIG. 9(b), a two-dot chain line indicates the position of the first lever 7' which is disposed on the locking side. In contrast with this, the first lever 7 disposed on the side opposite to the locking side is set in a position deviating as much as a phase difference "h" from the other lever 7' in the direction of closing the link.
As a result of this discrepancy in position, a torque for closing the link as shown by an arrow T acts on the first lever 7 disposed on the side opposite to the lock mechanism 20. The torque T is balanced with the above-stated lifting force for the cassette holder 6, so that the cassette holder 6, i.e., the tape cassette 1, can be held in a correct position.
The link mechanism of the conventional cassette mounting device which is arranged in the above-stated manner is generally configured in the form of X link. The first and second levers 7 and 8 which jointly form each X-shaped link are rotatably connected approximately in the middle part of the X-shaped link by means of the fulcrum shaft 9. Each of the levers 7 and 8 is arranged to swing on the connection shaft 10 or the shaft pin 13 at its one end and to make the shaft pin 11 or 15 slidably engage the cam slot 12 or 14 at the other end.
In the case of the conventional device described above by way of example, the cam slot 12 which is one of a pair of cam slots is formed in a mounting chassis, i.e., the sliding chassis 5, while the other cam slot 14 is formed in the second lever 8. Generally, the cam slot 12 is either formed aslant, as in the case of this example, to cause the shaft pin 11 to move also downward accordingly as the cassette holder 6 is moved down, or formed in parallel to the horizontal surface of the sliding chassis 5.
The balance of force between the locking side and the non-locking side of the link mechanism obtained in the locked state of the conventional device as shown in FIG. 9(b) will be considered. The torque T brought about by the phase difference "h" causes the shaft pin 11 of the first lever 7 to abut on the cam slot 12 of the sliding chassis 5. Therefore, a reaction force acting on the first lever 7 becomes F which is a resultant force of a component N perpendicular to the cam slot 12 and a frictional resistance .mu.N, as shown in FIG. 9(b). This reaction force F can be made into component forces Fx and Fy by resolving it into x and y components as shown also in FIG. 9(b). The component force Fx is exerted in the direction of moving the cassette holder 6 upward (as shown by an arrow u in the drawing) and thus decreases the torque T applied for holding the cassette holder 6. Besides, the direction of the reaction force F is disadvantageous in a case where some external force happens to exert a lifting force on the cassette holder 6. This results in a weaker holding force. Therefore, in order to accurately hold the tape cassette 1, it is necessary to increase the phase difference "h" of the first lever 7.
In the popped-up state shown in FIG. 9(a), on the other hand, when the cassette holder 6 is pushed down in this state, a reaction force applied from the cam slot 12 to the first lever 7 becomes a resultant force Fo of a vertical component No and a frictional resistance .mu.No. Meanwhile, a moment M of a counterclockwise swing of the first lever 7 taking place on the connection shaft 10 can be expressed as M=Lo.times.Fo, as shown in FIG. 9(a). Since the arm Lo of moment is long, the value of the moment M becomes large. Hence, the pushing-down force on the cassette holder 6 easily causes the first lever 7 to swing counterclockwise and the shaft pin 11 to move downward within the cam slot 12 in the direction of arrow d, so that the first lever 7 swings in the direction of closing the link. Therefore, there is only a weak resistance to the downward pushing force on the cassette holder 6. The feeling of a tape cassette mounting operation varies with the individual operator. However, with reduction in weight of the cassette mounting device attained, such a weak resistance tends to give a keeling of lack of rigidity (as the cassette holder 6 moves up and down too readily in response to a slight pushing force) to impair the touch of high-quality and reliability of the device.